Analysis system

• US 8,810,396 B2
• Filed: 12/22/2009
• Issued: 08/19/2014
• Est. Priority Date: 12/22/2008
• Status: Active Grant

• Current Assignee: S.P.M. Instrument AB
• Original Assignee: S.P.M. Instrument AB
• Inventors: Hedin, Lars-Olov Elis
• Primary Examiner(s): Bugg, George
• Assistant Examiner(s): Afrifa-Kyei, Anthony D
• Application Number:
  US13/141,407
• Publication Number:
  US 20110285532A1
• Time in Patent Office: 1,701 Days
• Field of Search: 340/540
• US Class Current: 340/540
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence
• CPC Class Codes: G01M 13/045 Acoustic or vibration analysis

Abstract

A method for analyzing the condition of a machine having a rotating shaft, includes:

receiving a digital input signal (I) having a first plurality (I_LENGTH) of sample values, the digital input signal (I) representing mechanical vibrations emanating from rotating the shaft so far as to cause occurrence of a vibration having a period of repetition (T_R);

• • dividing the received digital input signal (I) into a first signal portion (2070) and a second signal portion;
  • generating a digital output signal (O) having a second plurality (O_LENGTH) of samples, the second plurality (O_LENGTH) being a positive integer and lower than the first plurality (I_LENGTH); the digital output signal (O) being generated in response to the first signal portion (2070) and the second signal portion.

Claims

1. An apparatus for analysing a condition of a machine having a first part which is rotationally movable at a speed of rotation in relation to a second machine part, said apparatus including:

a sensor for monitoring said movable part so as to generate at least one analogue measurement signal including at least one vibration signal component dependent on a vibration movement of said rotationally movable part;

wherein said vibration signal component has a repetition frequency which depends on the speed of rotation of said first part;

said measurement signal including noise as well as said vibration signal component so that said measurement signal has a first signal-to-noise ratio value in respect of said vibration signal component;

an A/D-converter for generating a digital measurement data sequence in response to said measurement signal;

said digital measurement data sequence having a first sample rate;

a digital filter for generating a filtered measurement data signal in dependence on the digital measurement data sequence;

a digital enveloper for producing an enveloped signal in response to the filtered measurement data signal;

a decimator adapted to generate a decimated digital signal having a reduced sampling frequency dependent on said digitally enveloped signal;

an enhancer having an input for receiving said decimated digital signal;

said enhancer being adapted to produce an output signal sequence having a repetitive signal component corresponding to said at least one vibration signal component so that said output signal sequence has a second signal-to-noise ratio value in respect of said repetitive signal component;

said second signal-to-noise ratio value being higher than said first signal-to-noise ratio value; and

said enhancer being adapted to perform a correlation so as to produce said output signal sequence so that repetitive signal amplitude components are amplified in relation to stochastic signal components;

wherein

a) said enhancer is adapted to receive a first plurality of sample values of said decimated digital signal via said input;

b) said enhancer is adapted to store the received sample values in an input signal storage portion of a data memory associated with the enhancer;

c) said enhancer is adapted to set a variable t to an initial value;

d) said enhancer is adapted to calculate an output sample value S_MDP(t) for the variable value t by employing the equation;

2. The apparatus according to claim 1, wherein

said first decimator is adapted to reduce the sampling rate by an integer factor.

3. The apparatus according to claim 2, wherein

said first decimator has a port for receiving said integer factor.

4. The apparatus according to claim 2, wherein

said first decimator includes plural low pass Finite Impulse Response Filters;

said first decimator being adapted to perform said integer decimation in plural steps using said plural low pass Finite Impulse Response Filters;

wherein

each low pass Finite Impulse Response Filter is settable to a desired degree of decimation.

5. The apparatus according to claim 4, wherein

said first decimator being adapted to perform said integer decimation in four steps using four low pass Finite Impulse Response Filters having individual integer decimation factors M1, M2, M3 and M4 such that the total integer decimation of said first decimator equals

M=M1* M2* M3 *M4.

6. The apparatus according to claim 5, wherein

said first decimator includes a bank of mutually different Finite Impulse Response Filters which are combinable in several combinations to achieve the total integer decimation.

7. The apparatus according to claim 6, wherein

the maximum degree of decimation in the fourth step is five (M4=5), rendering a filter having 201 taps.

8. The apparatus according to claim 7, wherein

the Finite Impulse Response Filters in said first step, said second step and said third step have fewer than 201 taps.

9. The apparatus according to claim 8, wherein

the Finite Impulse Response Filters in said first step, said second step and said third step have 71 taps each or less than 71 taps.

10. The apparatus according to claim 9, wherein

the Finite Impulse Response Filter in said first step is adapted to provide a decimation factor M1=10, and

the Finite Impulse Response Filter in said second step is adapted to provide a decimation factor M2=10, and

the Finite Impulse Response Filter in said third step is adapted to provide a decimation factor M3=10, and

the Finite Impulse Response Filter in said fourth step is adapted to provide a decimation factor M4=4, so that a total decimation of M=4000 is achieved.

11. A method for analyzing a condition of a machine having a first part which is rotationally movable at a speed of rotation in relation to a second machine part, the method comprising the steps of:

(I) providing an apparatus comprising;

a sensor for monitoring said movable part so as to generate at least one analogue measurement signal including at least one vibration signal component dependent on a vibration movement of said rotationally movable part;

wherein said vibration signal component has a repetition frequency which depends on the speed of rotation of said first part;

said measurement signal including noise as well as said vibration signal component so that said measurement signal has a first signal-to-noise ratio value in respect of said vibration signal component;

an A/D-converter for generating a digital measurement data sequence in response to said measurement signal;

said digital measurement data sequence having a first sample rate;

a digital filter for generating a filtered measurement data signal in dependence on the digital measurement data sequence;

a digital enveloper for producing an enveloped signal in response to the filtered measurement data signal;

a decimator adapted to generate a decimated digital signal having a reduced sampling frequency dependent on said digitally enveloped signal;

an enhancer having an input for receiving said decimated digital signal;

said enhancer being adapted to produce an output signal sequence having a repetitive signal component corresponding to said at least one vibration signal component so that said output signal sequence has a second signal-to-noise ratio value in respect of said repetitive signal component;

said second signal-to-noise ratio value being higher than said first signal-to-noise ratio value; and

said enhancer being adapted to perform a correlation so as to produce said output signal sequence so that repetitive signal amplitude components are amplified in relation to stochastic signal components;

wherein

a) said enhancer is adapted to receive a first plurality of sample values of said decimated digital signal via said input;

b) said enhancer is adapted to store the received sample values in an input signal storage portion of a data memory associated with the enhancer;

c) said enhancer is adapted to set a variable t to an initial value;

d) said enhancer is adapted to calculate an output sample value S_MDP(t) for the variable value t by employing the equation;

12. A method for analyzing a condition of a machine having a first part which is rotationally movable at a speed of rotation in relation to a second machine part, the method comprising the steps of:

(I) providing an apparatus comprising;

a sensor for monitoring said movable part so as to generate at least one analogue measurement signal including at least one vibration signal component dependent on a vibration movement of said rotationally movable part;

wherein said vibration signal component has a repetition frequency which depends on the speed of rotation of said first part;

said measurement signal including noise as well as said vibration signal component so that said measurement signal has a first signal-to-noise ratio value in respect of said vibration signal component;

an A/D-converter for generating a digital measurement data sequence in response to said measurement signal;

said digital measurement data sequence having a first sample rate;

a digital filter for generating a filtered measurement data signal in dependence on the digital measurement data sequence;

a digital enveloper for producing an enveloped signal in response to the filtered measurement data signal;

a decimator adapted to generate a decimated digital signal having a reduced sampling frequency dependent on said digitally enveloped signal;

an enhancer having an input for receiving said decimated digital signal;

said enhancer being adapted to produce an output signal sequence having a repetitive signal component corresponding to said at least one vibration signal component so that said output signal sequence has a second signal-to-noise ratio value in respect of said repetitive signal component;

said second signal-to-noise ratio value being higher than said first signal-to-noise ratio value; and

said enhancer being adapted to perform a correlation so as to produce said output signal sequence so that repetitive signal amplitude components are amplified in relation to stochastic signal components;

wherein

a) said enhancer is adapted to receive a first plurality of sample values of said decimated digital signal via said input;

b) said enhancer is adapted to store the received sample values in an input signal storage portion of a data memory associated with the enhancer;

c) said enhancer is adapted to set a variable t to an initial value;

d) said enhancer is adapted to calculate an output sample value S_MDP(t) for the variable value t by employing the equation;

13. The method according to claim 12, wherein

the gear system includes a plurality of rotating parts which are rotating at mutually different rotational speed;

and

the sensor is adapted to generate the analogue electric measurement signal so that it includes at least one repetitive signal signature dependent on said mechanical vibrations such that the repetitive signal signature has a repetition frequency which depends on the speed of rotation of a part which is the origin of the repetitive signal signature;

wherein

the step of generating the machine condition includes the step of;

(IIIA) indicating the rotating part from which repetitive signal signature originates;

said indication being generated in dependence on the repetition frequency of the repetitive signal signature.

14. The method according to claim 12, wherein

the gear system includes a plurality of rotating parts which are rotating at mutually different rotational speed;

and

the sensor is adapted to generate the analogue electric measurement signal so that it includes at least one repetitive signal signature dependent on said mechanical vibrations such that the repetitive signal signature has a repetition frequency which depends on the speed of rotation of a part which is the origin of the repetitive signal signature;

wherein

the step of generating the machine condition includes the step of;

(IIIB) indicating a type of deteriorated condition from among a plurality of different types of deteriorated conditions;

said indicating step being performed in dependence on the repetition frequency of the repetitive signal signature.

15. The method according to claim 12, wherein

the gear system includes a plurality of rotating parts which are rotating at mutually different rotational speed;

and

the sensor is adapted to generate the analogue electric measurement signal so that it includes at least one repetitive signal signature dependent on said mechanical vibrations such that the repetitive signal signature has a repetition frequency which depends on the speed of rotation of a part which is the origin of the repetitive signal signature;

wherein

the step of generating the machine condition includes the step of;

detecting the repetition frequency of the repetitive signal signature; and

indicating a type of deteriorated condition in dependence on the detected repetition frequency;

wherein

the repetitive signal signature is indicative of at least one deteriorated condition selected from a group comprising;

a Bearing Inner Race damage, a Bearing Outer Race damage, and a teeth engagement error.